A126206 Number of 4's in the decimal expansion of 4^n.

0, 1, 0, 1, 0, 1, 1, 1, 0, 2, 1, 3, 0, 1, 2, 2, 2, 1, 1, 3, 0, 3, 3, 3, 2, 2, 2, 3, 1, 2, 2, 3, 4, 3, 1, 3, 3, 4, 2, 4, 2, 4, 2, 2, 3, 4, 3, 3, 3, 3, 2, 2, 3, 5, 2, 4, 2, 4, 4, 3, 3, 3, 4, 4, 6, 5, 5, 4, 2, 9, 5, 2, 4, 6, 4, 7, 4, 2, 5, 4, 3, 4, 8, 4, 7, 9, 2, 8, 4, 7, 3, 10, 9, 5, 3, 5, 8, 8, 3, 10, 4

Offset

0,10

Links

Robert Israel, Table of n, a(n) for n = 0..10000

Example

a(11)=3 because 4^11 = 4194304 with three 4's.

Maple

P:=proc(n) local i, k, x, y, w, cont; y:=4; k:=y; for i from 0 by 1 to n do x:=y^i; cont:=0; while x>0 do w:=x-trunc(x/10)*10; if w=k then cont:=cont+1; fi; x:=trunc(x/10); od; print(cont); od; end: P(100);
# Alternative:
map(n -> numboccur(4, convert(4^n, base, 10)), [$0..100]); # Robert Israel, Jul 18 2018

Mathematica

DigitCount[4^#, 10, 4]&/@Range[0, 150]  (* Harvey P. Dale, Feb 01 2011 *)

Crossrefs

Cf. A065710, A126205, A126207, A126208, A126209, A126210, A126211.

Sequence in context: A228786 A140699 A140256 * A307744 A119709 A328167

Adjacent sequences: A126203 A126204 A126205 * A126207 A126208 A126209

Keyword

nonn,base

Author

Paolo P. Lava and Giorgio Balzarotti, Dec 20 2006

Status

approved